Doctor Device For Fiber Web Machine And Doctor Arrangement In Fiber Web Machine

ABSTRACT

A doctor device includes blade devices ( 19 ) supported on holder devices ( 23 ). The holder devices ( 23 ) are for arranging the blade devices ( 19 ) in a fiber web machine to be placed in connection with a doctor blade ( 18 ) equipped with a blade holder ( 38 ). The blade devices ( 19 ) are supported aligned in a circumferential direction with edge areas ( 20 ) of the doctor blade ( 18 ). The holder devices ( 23 ) are arranged to be fastened in connection with the blade holder ( 38 ) so that the blade devices ( 19 ) extend further out than the doctor blade ( 18 ) to reduce the wear of the doctor blade ( 18 ).

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims priority on Finnish No. 2013, filed Apr. 1,2014, the disclosure of which is incorporated by reference herein.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The invention relates to a doctor device for a fiber web machine, whichdoctor device includes blade devices and holder devices for arrangingthe blade devices in a fiber web machine to be placed in connection withan adapted doctor blade equipped with a blade holder to the edge areasof said doctor blade. The invention also relates to a doctor arrangementin a fiber web machine.

Finnish patent number 110705 (U.S. Pat. No. 6,749,724) presents anarrangement in a fiber web machine. The arrangement is intended for theso-called wet end of a fiber web machine, where material such as fibersand fillers adhere to the rolls from the moist web and especially fromits edges. Accumulations of this kind result in, among other things, theweb sticking to the roll surface, which increases web breaks and thusdisturbs production. The patent suggests that short blade devices beplaced after the doctor blade that is supported to a blade holder, whichblade devices enhance the doctoring efficiency of the arrangement at theedges of the doctor blade, i.e. at the edge areas.

In practice, it is challenging to place a prior art arrangement in thefiber web machine. In fact, the above-mentioned patent describes thearrangement only in principle, without any holder devices for the bladedevices. Moreover, the arrangement is unsuited to other locations suchas the finishing section, where local fouling of a roll also occurs. Asan example, after coating some coating slip accumulates on the surfaceof a roll, especially at the edge areas of the doctor blade. In such aposition, the doctor blade of the application presented in said patentwould wear rapidly and unevenly in the same way as a doctor bladecurrently wears in said position. In this case, streaks remain on thesurface of the roll especially at the edge areas, and the streaks remainvisible in the end product, too. Moreover, a worn doctor blade needs tobe replaced frequently, which causes extra costs. In practice, the fiberweb machine must be stopped for the duration of the replacement of thedoctor blade, which shortens the efficient production time.

SUMMARY OF THE INVENTION

The object of this invention is to accomplish a new type of a doctordevice for a fiber web machine, which doctor device can be used forintensifying the efficiency of the doctor arrangement and at the samefor reducing the uneven wear of the doctor blade. Another object of theinvention is to accomplish a new type of a doctor arrangement for afiber web machine, where the doctoring efficiency of the doctorarrangement is better than previously and where the replacement intervalof the doctor blade is longer than previously. A characteristic featureof the doctor device according to the invention is that the holderdevices are arranged to be fastened in connection with a blade holder sothat the blade devices are further out than the doctor blade.Correspondingly, a characteristic feature of the blade arrangementaccording to the invention is that the blade devices are arranged beforethe doctor blade in the direction of rotation of the roll. In practice,the blade devices remove a significant portion of the material at theedge areas of the doctor blade even before the doctor blade. In thiscase, the short blade devices wear, but the costs caused by theirreplacement are considerably smaller than the cost of replacement of afull-length doctor blade. Moreover, the blade devices can be servicedeven during production. In this way, it is possible to avoid qualitydeviations in the end product and to achieve as uninterrupted productionas possible.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described below in detail by making reference to theenclosed drawings that illustrate an embodiment of the invention.

FIG. 1 shows the finishing section of a fiber web machine.

FIG. 2a shows a doctor arrangement according to the invention.

FIG. 2b shows a partial magnification of FIG. 2 a.

FIG. 3a shows a doctor arrangement according to the invention seen fromthe tending side diagonally from the back.

FIG. 3b shows the doctor arrangement of FIG. 3a seen diagonally from thefront.

FIG. 3c shows a doctor arrangement according to the invention seen fromthe drive side diagonally from the front.

FIG. 4a shows a doctor arrangement according to the invention seenagainst the machine direction.

FIG. 4b shows the doctor arrangement of FIG. 4a seen in the machinedirection.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a finishing section of a fiber web machine which is knownas such. Only the last drying cylinder 11 is presented of the dryersection that precedes the finishing section. The web forming machinesare usually paper or board machines. The consecutive production sectionsshown in FIG. 1 are—in addition to the dryer section 10—pre-calendering12, coating 13 and calendering 14, after which the finished web isreeled with the reel 15. This application represents so-called onlinefinishing, where the web is fed from the dryer section directly tofinishing without re-reeling. In order to minimize production losses, itis important to have disturbance-free production from the wet end to thereel.

Marked with X in FIG. 1 are example positions where the doctorarrangement according to the invention is preferably used. Generallyspeaking, roll 16 of FIG. 2a included in the fiber web machine isequipped with the doctor arrangement. The doctor arrangement includes adoctor blade 18, which is here supported to the doctor beam 17 arrangedin connection with the roll 16 (FIG. 2a ). The doctor blade is primarilyused for keeping the surface of the roll clean, but in certain positionsit is also used for guiding the web into a pulper in a web breaksituation. The doctor beam extends essentially across the width of theentire roll, and it is usually supported by bearings at both ends. Byturning the beam 17, the doctor blade 18 can be placed against thesurface of the roll 16 and also away from it. The beam 17 canpotentially also be moved in the axial direction.

The doctor arrangement also includes blade devices 19 which are separatefrom the doctor blade 18 and which are arranged at both edge areas 20 ofthe doctor blade 18 (FIGS. 4a and 4b ). In practice, the edge areas ofthe doctor blade correspond to the edge areas of the roll. In the mostchallenging position, the roll 16 is a drying cylinder 21 (indicated inFIG. 1), which is placed after a coating station 22 included in a fiberweb machine. The surface of the drying cylinder is hot, whichcontributes to the sticking of the coating slip. The doctor arrangementaccording to the invention works in this position, too, and remainsoperational for a longer period than previously.

The coating slip contains substances such as kaolin, calcium carbonateor talc. These are very abrasive substances. Moreover, they accumulateeasily on the surface of the roll, which makes the above-describeddoctor positions demanding. Doctor blades made even completely of carbonfiber are used in prior art arrangements. Such doctor blades are hardand endure wear, but they are expensive. Despite their wear-resistance,the doctor blades wear unevenly, so their replacement intervals areshort.

This is why in the invention the blade devices 19 are arranged beforethe doctor blade 18 in the direction of rotation of the roll 16. In thisway, the blade devices 19 first touch the material that has accumulatedon the surface of the roll. In this case, most of the wear impact isdirected at the blade devices, while the actual doctor blade 18 is wornless. The doctor blade consequently wears more evenly than previously,which extends the service life of the doctor blade and reduces its needfor replacement. At the same time, the material can be removed moreefficiently from the surface of the roll 16.

FIG. 2a shows the roll 16 in part only. Correspondingly, FIG. 2billustrates a prior art doctor blade 18 and doctor beam 17 with a brokenline, and the doctor device according to the invention is illustratedwith a solid line. The doctor device is intended for a fiber webmachine, and it includes blade devices 19 and holder devices 23. Theholder devices 23 are intended for the placement of the blade devices 19in connection with the doctor blade 18 included in the fiber webmachine, to the edge areas 20 of said doctor blade 18. In the invention,the holder devices 23 are arranged to be fastened in connection with theblade holder 38 so that the blade devices 19 are further out than thedoctor blade 18. With respect to the fastening point of the doctorblade, the blade devices extend further out than the doctor blade, bothin the blade direction and radially.

With respect to the roll, the holder devices 23 are thus arranged forthe placement of the blade devices 19 before the doctor blade 18 in thedirection of rotation of the roll 16. In this case, by means of theholder devices 23 the doctor device can be placed in connection with thedoctor blade 18 so that the blade devices 19 are located before thedoctor blade. In the invention, the blade devices 19 are also preferablysupported to said doctor beam 17. In other words, the holder devices 23include a support structure 24, which has connecting devices 34′ forfastening to the doctor beam 17 arranged to support the doctor blade 18.In this case, the blade devices can be simply added to an existingdoctor arrangement, and to put it more precisely, by fastening theconnecting devices to the doctor beam.

FIGS. 3a to 3c show one end of the doctor arrangement at a time. Theholder devices 23 according to the invention include a blade holder 26,which is fastened to a support strip 27. The support strip 27 is atleast as long as the blade holder 26. The blade holder as such can bedifferent from that presented, but here the applicant's own modelprovided with one loading hose has been used.

The supporting of the blade devices is also of a new type: the supportstructure 24 is fastened to one end of the holder devices 23. In otherwords, the holder devices are supported in a projection-type manner,whereby the operation of the doctor blade 18 remains unchanged. In theapplication presented, each blade device 19 includes a support arm 28.Here, the support arm 28 is connected to the support strip 27 by meansof two connectors 29. There can also be more numerous connectors, orsome other applicable support structure is used in the supporting. Thefastening is carried out by means of two pairs of bolts 30, for whichbolts there are elongated holes 37 in the support strip 27. In thiscase, the support strip 27 can be adjusted with respect to the supportarm 28. More generally speaking, there are adjusting devices 31, shownin FIG. 2b , between the holder devices 23 and the support structure 24.Adjustment is needed primarily in the installation of the doctor device.During operation, the blade devices are loaded by means of a loadinghose 32 shown in FIG. 2 b.

The installation of the doctor device according to the invention inconnection with the doctor blade has been designed to be especiallyeasy. In the invention, as shown in FIGS. 3a-3b the blade devices 19,more precisely the support arm 28, is fastened to the doctor beam 17using the same fastening devices 34 that support the doctor blade 18. Inother words, there is a similar hole pitch 33 in the support arm 28 forthe fastening devices 34 as in the doctor holder 38 of the doctor blade18. In this way, the doctor device can be fastened as long as bolts 34′that are longer than normally are used at the support arm 28. In FIG. 3c, there are six such bolts, only two of which are illustrated.

It has also been possible to keep the manufacturing costs of the doctordevice at a reasonable level. The holder devices 23 according to theinvention are symmetrical. In other words, there are almost identicalblade holders at both ends of the roll, while the support arms 28 of thedoctor devices are minor images of each other. In this case, spare partssuch as a short doctor blade 35 can be used at either end. Thesymmetrical design is illustrated especially in FIG. 4a , where thedoctor arrangement is viewed against the machine direction. At both endsof the short blade holder 26, there is a finger plate 36 by which theblade holder 26 can be moved. Moreover, the support strip 27 has twosets of elongated holes 37 for fastening to the support arm 28 as shownin FIG. 3a . There are also compressed air connections at both ends ofthe loading hose 32, and compressed air supply is connected to theoutermost of these connections. In this case, the doctor arrangement canbe composed of standard components by arranging two doctor devicesaccording to the invention in connection with an existing doctor blade,on the same doctor beam.

FIGS. 4a and 4b might suggest that the blade devices 19 areunnecessarily long. In practice, the length of the holder devices 23 is800 to 1,200 mm. Moreover, the blade devices 19 extend clearly beyondthe edge areas 20. In practice, 40 to 60 percent of the length of theblade devices 19 extends beyond the edge areas 20. In this case, thefinger plate 36 extends to a safe distance from the roll. In otherwords, the blade holder can be moved by the finger plate also duringproduction. This is why, if the short doctor blade wears locally, it canbe moved somewhat manually, whereby the best doctoring result can beachieved at the most critical location. Moreover, the moving is possiblewithout a safety risk. By depressurizing the loading hose and, ifnecessary, by using vacuum, the short doctor blade can be detached fromthe surface of the roll and hence the blade holder can be moved. Ifnecessary, the entire blade holder with the doctor blade can be pulledoff for service and replacement. The part beyond the roll can also beutilized by exchanging the short doctor blades on the tending and drivesides with each other. In this way, even a short doctor blade can beutilized over its entire length. In the same manner, parts of the doctorblade 18 that have worn unevenly can be removed, and it can be used forreconditioning several short doctor blades 35. As an example, the widthof a roll is currently from 4 to 10 meters, while the length of theblade devices according to the invention is from approximately 0.5meters to approximately 1 meter.

Above is a description of one example of a doctor device according tothe invention and of its utilization in a doctor arrangement. Generallyspeaking, the doctor device according to the invention comprises a firstblade holder 26, which is short. A short doctor blade 35 is supported tothis short blade holder 26. The short doctor blade 35 constitutes partof the blade devices 19. Both the short blade holder and the shortdoctor blade extend over only a part of the width of the roll surface tobe doctored, preferably over its edge areas. The doctor blade 18included in the doctor arrangement and the blade holder 38 that supportsthe doctor blade 18 extend essentially over the entire width of the rollto be doctored.

The doctor device according to the invention is simple and compact.Components proven in practice can be applied to it. If necessary, forexample the blade holder is reinforced to increase the load resistance.The doctor device can be placed in connection with various types ofdoctor blades. Two doctor devices can be used for updating a doctorarrangement quickly to a new level. In this way, the doctoring result isimproved even though the replacement interval of the doctor bladeextends at the same time. The effective production time is thusmaximized while at the same time minimizing the maintenance costs. Inconjunction with the installation of doctor devices, a modern bladeholder with a new type of doctor blade is preferably replaced in thedoctor beam. In this way, the overall doctoring result of the doctorarrangement is improved and serviceability is facilitated.

1-13. (canceled)
 14. A doctor device for a fiber web machine having aroll with a cylindrical surface to be doctored which roll defines acircumferential direction along which the roll rotates, a doctor blade(18) engageable with the roll cylindrical surface, wherein the doctorblade (18) is mounted in a first doctor blade holder to a doctor beamwhich extends in a cross machine direction, the doctor blade having inthe cross machine direction, a first end edge and a second end edge, anda middle between the first end edge and the second end edge, wherein anoutward direction is defined between the middle and the first end edgeand between the middle and the second end edge, the doctor devicecomprising: two blade devices (19), wherein each blade device is mountedto a holder device (23) which is arranged to fastened one of the bladedevices to the first blade holder (38) of the doctor blade (18); whereinthe holder devices (23) are arranged to be connected to the doctor beam(38) aligned with an edge area containing one of the first end edge andthe second end edge of the doctor blade (18); wherein the holder devices(23) are arranged to be fastened to the blade holder (38) so that aportion of each blade device is further out in the outward directionthan the doctor blade (18); and wherein each blade device when mountedto the first blade holder extends further out than the doctor blade sothat the blade devices are positioned to engage the roll before thedoctor blade in the circumferential direction.
 15. The doctor device ofclaim 14 wherein the each of the holder devices (23) includes a supportstructure (24) which has connecting devices for fastening to the doctorbeam (17).
 16. The doctor device of claim 14 wherein each of the holderdevices has two ends, and further comprising a support structure (24)fastened to one end of the holder devices, wherein the support structurehas connecting devices for fastening to the doctor beam (17).
 17. Thedoctor device of claim 14 wherein the two holder devices (23) aresymmetrical about a plane passing between said two holder devices. 18.The doctor device of claim 14 wherein the holder devices define a lengthof 800 to 1,200 mm in the cross machine direction.
 19. The doctor deviceof claim 15 further comprising adjusting devices (31) between the holderdevices (23) and the support structures (24).
 20. A doctor arrangementin a fiber web machine having a roll to be doctored, the roll definingan axis along which the roll is supported to rotate and along which theroll extends to define a roll width, the axis defining an axialdirection, and the roll defining a circumferential direction of rotationof the roll, the doctor arrangement comprising: a doctor blade (18)which extends essentially across the entire roll width, wherein thedoctor blade has in the axial direction a first end edge and a secondend edge; two blade devices (19) each of which is separate from thedoctor blade (18), wherein each blade device is arranged aligned with anedge area containing one of the first end edge and the second end edge;and wherein the blade devices and the doctor blade are arranged so thatwith respect to the cylindrical surface which the blade devices anddoctor blade are arranged to engage, the blade devices (19) are arrangedbefore the doctor blade (18) in the direction of rotation of the roll(16).
 21. The doctor arrangement of claim 20 further comprising a doctorbeam, and wherein the blade devices (19) are supported to the doctorbeam (17) to which the doctor blade is supported by fastening devices.22. The doctor arrangement of claim 20 wherein the fiber web machine hasa coating station (22) and wherein the roll (16) is a drying cylinder(21) which is placed after the coating station in the fiber web machine.23. The doctor arrangement of claim 20 wherein the blade devices (19)extend beyond the edge areas (20).
 24. The doctor arrangement of claim23 wherein the blade devices (19) define a length and 40 to 60 percentof the length of the blade devices (19) extends beyond the edge areas(20).
 25. The doctor arrangement of claim 21 wherein each blade device(19) includes a support arm (28) which is fastened to the doctor beam(17) using at least some of the fastening devices (34) that support thedoctor blade (18).
 26. A doctor arrangement for a fiber web machinehaving a coating station and a dryer roll having a cylindrical surfacearranged after the coating station, the dryer roll defining acircumferential direction along which the dryer roll rotates; the doctorarrangement comprising: a main doctor blade (18), wherein the maindoctor blade (18) is supported in a first blade holder (38) which ismountable to a doctor beam which extends in a cross machine direction;wherein the main doctor blade has in the cross machine direction, afirst end edge and a second end edge, and a middle between the first endedge and the second end edge, wherein an outward direction is definedbetween the middle and the first end edge and between the middle and thesecond end edge; two short doctor blades each of which is shorter thanthe main doctor blade (18) and each short doctor blade is supported in aholder device which is arranged to fasten one of the short doctor bladesto the doctor beam (18); wherein the short doctor blades and the maindoctor blade are arranged so that with respect to the cylindricalsurface to which the blade devices and doctor blade are arranged toengage, the short doctor blades (19) are arranged before the main doctorblade (18) in the circumferential direction of rotation of the roll(16); wherein the holder devices (23) are arranged supported on thedoctor beam aligned with an edge area containing one of the first endedge and the second end edge of the doctor blade (18); wherein theholder devices (23) are arranged to be fastened to the doctor beam sothat a portion of each short doctor blade is further out in the outwarddirection than the main doctor blade (18); and wherein each short doctorblade extends further out than the main doctor blade so that the shortdoctor blades are positioned to engage the dryer roll before the maindoctor blade in the circumferential direction.
 27. The doctorarrangement of claim 26 wherein the main doctor blade is supported onthe doctor beam by fastening devices.
 28. The doctor arrangement ofclaim 26 wherein the short doctor blades extend beyond the edge areas inthe outward direction.
 29. The doctor arrangement of claim 26 whereinthe short doctor blades define a length, and 40 to 60 percent of thelength of the short doctor blade extends beyond the edge areas in theoutward direction.
 30. The doctor arrangement of claim 27 wherein eachholder device includes a support arm which is fastened to the doctorbeam using at least some of the fastening devices that support the maindoctor blade.